Cardiovascular disease is the leading cause of death in both developed and developing countries. It accounts for 30% of all global deaths. Due to the aging population in the world, the number of patients with cardiovascular disease is expected to dramatically increase. Coronary artery disease (CAD) is the most prevalent cardiovascular disease, caused by the build-up of plaque inside the coronary artery. The plaque narrows the artery and eventually impacts the blood supply to the heart. As a result, CAD has been linked to the development of cardiovascular-related events and accounts for 45% of deaths due to cardiovascular disease.
Therefore characterization and quantification of the significance of coronary stenosis is of the utmost importance for patient management to prevent mortality from CAD. In clinical cardiology, both anatomical and hemodynamic indices are commonly applied to quantify the severity of CAD. The rapid developments of non-invasive imaging technologies, such as computed tomography angiography (CTA), are valuable, for their relatively lower cost and medical complications. Most of the non-invasive imaging technologies focus on anatomical significance and diameter stenosis (DS) is calculated as an index. DS expresses the diameter of a stenosed region relative to a “normal” segment, but it provides little or no hemodynamic information of the stenosis. The current gold standard to assess the functional severity of coronary artery stenosis is fractional flow reserve (FFR). FFR can be calculated as the ratio of the pressure distal to a coronary stenosis to aortic pressure at the hyperemia state. When the coronary stenosis leads to FFR≤0.80, revascularization is commonly recommended. However, FFR can only be measured via invasive coronary catheterization, which carries higher medical cost and some complications.
The limitations of invasive coronary catheterization motivates us to find a novel approach to assess the functional significance of coronary artery stenosis directly from medical images obtained with non-invasive imaging technologies.
In the current clinical practice, cardiologists and radiologists only have the anatomical information of the coronary artery stenosis from CTA images alone. There is a lack of information on the functional significance of the coronary lesion. However, anatomical index of diameter stenosis (DS) was found to lead to a much higher false positive rate relative to FFR and tends to overestimate the significance of the stenosis for ischemia.